"tenho mais que fazer" that is to say "I have more important things to do"

There's an expression I often use when I speak in portuguese that is:

"Tenho mais que fazer".

It means something like "I have more important things to do (so I'm not gonna bother wasting my time and energy and preoccupation on the current issue)".

For example. Trying to make someone understand that they way they acted is not the best, ie showing we care, and showing that we want to make that person better. But that person showing no respect to even listen to us.

"I'm here trying to help you and you show no appreciation or willing to listen whatsoever, so I "tenho mais que fazer"".

I found this expression interesting because it shows our worry with not wasting time and our self-respect.

In Portugal this is rather normal "thing" to do, but here in Japan I only notice it in other people in crosswalks. Taking micro shortcuts when walking.
Like why always go straight and follow the "correct" way (for instance when you are reaching the end of the crosswalk) and waste some seconds going straight and then turn right/left when you could save time and start going more diagonally and reach the new "path" faster. In the crossway example is only applies in like the last 1 meter or so before reaching its end.

I do this so naturally that I don't really notice. I mean, before taking the micro shortcut I look at the possibilities and do the "math" for nano seconds and chose the fastest way to go.
But I had never thought about even thinking about this. Never thought it could be relevant or useful. But now that I see myself dealing with people who have different ways to do things, and now that I'm the "exception to the rule", or the "different" one around here, that these little things get more noticeable.


The "Tenho mais que fazer" mindset, I think it could be applied to this everyday short cutting way to walk or do things.